In the normal mode, these devices are functionally equivalent to
the 'F245 and 'ABT245 octal bus transceivers. The test circuitry can
be activated by the TAP to take snapshot samples of the data
appearing at the device pins or to perform a self test on the
boundary-test cells. Activating the TAP in normal mode does not
affect the functional operation of the SCOPETM octal bus
transceivers.

Data flow is controlled by the direction-control (DIR) and
output-enable () inputs. Data
transmission is allowed from the A bus to the B bus or from the B bus
to the A bus, depending on the logic level at DIR. The output-enable
() input can be
used to disable the device so that the buses are effectively
isolated.

In the test mode, the normal operation of the SCOPETM
bus transceivers is inhibited and the test circuitry is enabled to
observe and control the I/O boundary of the device. When enabled, the
test circuitry can perform boundary-scan test operations as described
in IEEE Standard 1149.1-1990.